Custom Indicator unable to find line attributes in the passed datafeed; 'Lines_LineSeries_LineIterator_DataAccessor_Indicat' object has no attribute

[monke]

I created a custom indicator which I intend to use on multiple data feeds. In the init method of my strategy, I created a line object 'spread' for the feeds (it will be used in the indicator). However, the line attribute is not being found when I use it in my indicator
'Lines_LineSeries_LineIterator_DataAccessor_Indicat' object has no attribute 'spread'

Here is my code:

class em_fit_converter(bt.Indicator):
    lines = ('A','B','C','D','G','H','k')
    params = (('period', 50),)
    W = 50 #trailing window used for em_fit in everyday calculation
    max_iter = 1000
    
    
    def next(self):
        n = len(self.datas) - 1
        self.lines.A[0], self.lines.B[0], self.lines.C[0],
        self.lines.D[0], self.lines.G[0], self.lines.H[0],
        self.lines.k[0] = em_fit(self.spread.get(size = self.p.period), self.market_rets.get(size = self.p.period), 
                                 init_params, num_iter = max_iter)

class testStrategy(bt.Strategy):
    
    
    def __init__(self):
        
        n = len(self.datas) - 1                           #will be used to point to log market returns (last data feed)
        
        for i,d in enumerate(self.datas[0:n]):                 #data order in self.datas same as that of stocks listed in the pairs array
            if i%2 == 0:                                  #for even indices in self.datas aka first stock in every pair
                self.spread = self.datas[i].close - self.datas[i+1].close
                self.market_rets = self.datas[n].close
                self.lines.values = em_fit_converter(self.datas[i])
                self.theta = self.values.lines.B/(1 - self.values.lines.A)
                self.true_spread = self.spread - self.values.lines.D * self.datas[n].close
                self.cum_sum_true_spread = sum(self.true_spread.get(size = 5))
                
    def next(self):
        
        for i,d in enumerate(self.datas[0:n]):
            if i%2 == 0:
                if self.cum_sum_spread < self.theta:
                    self.buy(data = d, size = 10)
                    self.sell(data = self.datas[i+1], size = 10)
                    
                if self.cum_sum_spread > self.theta:
                    self.sell(data = d, size = 10)
                    self.buy(data = self.datas[i+1], size = 10)

Here is how im adding the indicator, strategy etc. to cerebro (I have not included the code that adds the data feeds here)

cerebro.addstrategy(testStrategy)
cerebro.addindicator(em_fit_converter)
cerebro.addanalyzer(bt.analyzers.SharpeRatio, _name = 'sharpe')
test = cerebro.run(runonce = False)

This is the error:
AttributeError: 'Lines_LineSeries_LineIterator_DataAccessor_Indicat' object has no attribute 'spread'

Any help is appreciated. Thanks in advance!